The unit on Neurocytology and Physiology, directed by Douglas Fields, is investigating how expression of genes known to regulate proteins that are important in development of the nervous system can be regulated by specific patterns of neuronal impulses in neurons, and thereby provide an important influence on the developing structure and function of the nervous system. Effort is now focused on: (1) identifying important biological consequences of gene products regulated by neural impulse activity; (2) identifying the signaling mechanisms responsible for regulating gene expression by specific patterns of membrane depolarization; (3) understanding the involvement of cell adhesion molecules (CAMs), gene expression, and activity patterns in synaptic plasticity. Changes in nervous system structure and function are influenced by neural impulse activity during development. It is known that expression of specific genes is necessary for persistent changes in the nervous system, but it is not clear how specific patterns of neural impulses can regulate the expression of genes important in development and plasticity of the nervous system. Our research indicates that the temporal dynamics of intracellular signaling cascades are critical in decoding the temporal aspects of action potential activity. Cell adhesion molecules have a major influence on development of the nervous system. Experiments to identify molecules that may participate in activity-dependent plasticity show that electrical activity of neurons in culture can influence the expression of neural cell adhesion molecules. Moreover, different CAMs are regulated by different patterns of impulse activity. The cell adhesion molecule L1 is down-regulated by 0.1 Hz stimulation, but not 1 Hz stimulation of DRG neurons. N-cadherin is down-regulated by both frequencies of firing, and NCAM expression is not altered by either pattern of firing. Activity-dependent changes in CAM expression produce several functional and structural changes in neural networks in culture that could be important in remodeling the nervous system during development.